Lytocarpia billardi (Bale 1914)

Watson, Jeanette E., 2018, Some Hydroids (Cnidaria, Hydrozoa) from the Great Australian Bight in the collection of the South Australian Museum, Zootaxa 4410 (1), pp. 1-34 : 25-26

Lytocarpia billardi (Bale 1914)

Figure 10A–E

Aglaophenia billardi Bale, 1914a: 33 , pl. 3, fig. 3, pl. 6, fig. 3.

Material examined. SAM H2319, SAM H2333, preserved material; 200 km south-west of Eucla, trawl, 175 m; coll: R. Southcott. SAM H2540, preserved material; two microslides (SAM H2596, H2597). PIRSA Stn BBMP2c.

Description. Several fertile colonies and colony fragments, the largest colony 10 cm high growing from a fibrous hydrorhizal rootstock. Proximal half of stem ahydrocladiate, upper part with two sets of subdichotomous branches to 8 cm long, branches fascicled throughout without division into internodes. Hydrocladia alternate, to 10 mm long, borne on a short apophysis on frontal tube of stem, hydrocladial internodes distinct.

Hydrotheca long, tubular, abcauline wall straight to weakly convex, a small abcauline septum near posterior, adcauline wall weakly convex, a thick forwardly curved septum passing about halfway into hydrotheca from adcauline posterior, connecting with a short thick septum of variable length at base of hydrotheca into hydrocladium. Margin of hydrotheca with a long sharp anterior rostrum and four pairs of cusps, the first pair prominent, the second and third pair very low, the last pair behind lateral nematothecae.

Median nematotheca straight, tubular, about half length of hydrotheca, adnate, terminal orifice sinuous, open down to hydrotheca. Lateral nematotheca tubular to spanner-shaped (depending on angle of view), widening from base to margin, orifice deeply excavated down to hydrothecal margin, a short thick septum extending into hydrocladium from base.

Largest corbula 2 mm long x 1 mm wide, closed, gonocladium of four proximal internodes each bearing a nematotheca, leaflets fringed with nematothecae of similar shape and size to laterals.

Colour of preserved material pale honey brown, hydrocladia paler.

Remarks. The Bale collection in Museum Victoria contains 16 microslides of Lytocarpia billardi (Bale 1914) , ten of which are collectively registered NMV F58658 , the remaining six collectively registered as NMV F58659 . All are designated syntypes by Stranks (1993). Microslides of the series NMV F58658 are labelled in Bale’s handwriting “Great Australian Bight, 40–100 fthms, Endeavour, 1913”. A slide with Bale’s catalogue number “283”, displays a female corbula, and “284”, displays a male corbula. The series F58659 labelled “Great Australia Bight, Endeavour, 1912” contains a slide with Bale’s catalogue number 334, but lacks information on collection depth. All slides are Canada-Balsam mounted, unstained and in good condition; however the specimens are fading into the dark background of the mountant making detailed examination difficult. I select a microslide from the F58658 series displaying both male and female corbulae as lectotype of Lytocarpia billardi .

The single anterior rostrum of Lytocarpia billardi distinguishes it from Lytocarpia crucialis ( Lamouroux, 1816) which, according to Billard (1907) has a bifid rostrum. The slender, elongate hydrotheca set at an acute angle of 30–35° to the hydrocladial axis distinguishes L.billardi from L. tasmanica ( Bale, 1914a) , the hydrotheca of which is set at a more obtuse angle.

The slender corbulae (5–11 mm long x 1.2–1.5 mm wide) are probably male and the larger corbulae (6–15 long x 2 mm wide) probably female but the gonophores are too deteriorated for further identification. The rows of large nematothecae bordering the leaflets have deeply excavated margins identical to the laterals.

Distribution. Great Australian Bight; this is the second record of the species.

Figures

FIGURE10A–E.Lytocarpia billardi (Bale, 1914).A, fertile colony.B, hydrothecae.C, hydrotheca, anteriorview.D, proximal view of corbula with gonocladium.E, mid-section of corbula.